Found 15 talks width keyword dust

Abstract

Until the advent in the late 1990’s of sensitive submillimetre arrays such as SCUBA, it was generally thought that the main sources for the interstellar dust found in galaxies were the dusty outflows from evolved AGB stars and M supergiants, although a dust contribution from supernovae had long been predicted on theoretical grounds. The detection at submillimetre wavelengths of very large dust masses in some high redshift galaxies emitting less than a billion years after the Big Bang led to a more serious consideration of core-collapse supernovae (CCSNe) from massive stars as major dust contributors. KAO and Spitzer mid-infrared observations confirmed that CCSN ejecta could form dust but it was not until the Herschel mission and subsequent ALMA observations that direct evidence has been obtained for the presence of significantly large masses of cold dust in young CCSN remnants. As well as using infrared spectral energy distributions to measure the amounts of dust forming in CCSN ejecta, dust masses can also be quantified from the analysis of red-blue asymmetries in their late-time optical emission line profiles. I will describe current results from these methods for estimating ejecta dust masses, and their implications.

Abstract

One of the important questions in extragalactic astronomy concerns the debate between nature and nurture scenarios. Are the observed galaxy local properties the end product of the different conditions at birth or the product of the interactions, or other local processes, since a galaxy is not an isolated object? In this talk I will present the results of the analysis of some galaxy properties, morphologies and mass functions, obtained comparing, for the first time in a consistent manner, galaxies in the widest range of environments at low redshift (groups, clusters, binary systems, isolated galaxies). The aim was to understand the most important factors that drive galaxy evolution, trying to disentangle the importance of galaxy mass and global environment.

In addition I will present the first results concerning the two projects in which I am involved at IAC: the ALBA project, aimed to explore the signs of a proto-cluster at z~6.5, and the analysis of dust emission of a sample of local tadpole galaxies.

Abstract

In order to understand galaxy formation it is crucial to obtain sensitive observations of the emission of dust and molecular gas both of which constrain the on-going star formation or AGN activity and the future potential of the galaxy to grow. Constraining the growth of ensemble of galaxies in the distant universe and not simply the most active ones, is one of the primary goals of current and planned (sub)mm facilities such as ALMA or SPICA. I will discuss two major questions in galaxy formation and assembly: 1) are dusty galaxies vigorously forming stars embedded within large scale structures at z>1.5; and 2) do dusty starbursts exist at the highest redshift. To shed light on these obscure topics, I will present our on-going observations of dust and molecular gas with a number of different (sub)mm facilities such as Herschel, APEX, IRAM or ALMA of one important star forming galaxy population in the distant universe: submillimeter selected galaxies (SMGs). My presentation will be complemented by our recently initiated census of the molecular gas reservoirs of nearby galaxies with optical IFU coverage. The local analogs serve as a reference sample for current and future studies of high-z galaxy populations.

Abstract

Evolved stars are factories of cosmic dust. This dust is made of tiny grains that are injected into the interstellar medium and plays a key role in the evolution of astronomical objects from galaxies to the embryos of planets. However, the processes involved in dust formation and evolution are still a mystery. The increased angular resolution of the new generation of telescopes will provide for the first time a detailed view of the conditions in the dust formation zone of evolved stars, as shown by our first observations with ALMA. The aim of the NANOCOSMOS project is to take advantage of these new observational capabilities to change our view on the origin and evolution of dust. We will combine astronomical observations, modelling, and top-level experiments to produce stardust analogues in the laboratory and identify the key species and steps that govern the formation of these nanoparticles. We will build two innovative setups: the Stardust chamber to simulate dust formation in the atmosphere of evolved stars, and the gas evolution chamber to identify novel molecules in the dust formation zone. We will also improve existing laboratory setups and combine different techniques to achieve original studies on individual nanoparticles, their processing to produce complex polycyclic aromatic hydrocarbons, the chemical evolution of their precursors and their reactivity with abundant astronomical molecules. Our simulation chambers will be equipped with state-of-the-art in situ and ex situ diagnostics. Our astrophysical models, improved by the interplay between observations and laboratory studies, will provide powerful tools for the analysis of the wealth of data provided by the new generation of telescopes.

The synergy in NANOCOSMOS between astronomers, vacuum and microwave engineers, molecular and plasma physicists, surface scientists, including both experimentalists and theoreticians is the key to provide a cutting-edge view of cosmic dust.

Abstract

R Coronae Borealis (RCB) stars are the more prominent group of high luminosity hydrogen deficient stars that are rich in carbon and helium. They also show characteristic irregular light drops of several magnitudes (between 3 and 8 magnitudes) at unpredictable times, caused by expulsion of self-made clouds of dust. They range in surface temperatures from 4500 K to 20000 K. Some of them seem to have made even such complex molecules like fullerenes (C60) in their circumstellar regions. Neither their evolutionary history nor the dust formation mechanism are well understood. Two scenarios that have been suggested are that the present stars are a result of merger of two white dwarfs (CO+He) or a post born-again (AGB) giant that is surviving after a final helium shell flash. The talk would describe the RCB properties and highlight the problems and challenges they pose in understanding their origins and dust production.

Abstract

It is now clear that supermassive black holes (M>1e6 Msun) live in the center of most (all) galaxies, including our own Milky Way. Furthermore, the energy released during the growth of this black hole is a critical ingredient in understanding galaxy formation and evolution. In this talk, I will show what we know about how, when and where these supermassive black holes are acquiring their masses. In particular, I will focus on the effects of obscuration, as it is now clear that the majority of this black hole growth is hidden from our view by large amounts of gas and dust. I will present statistical evidence suggesting that while most nuclear activity is triggered by internal secular processes, the most violent episodes are linked to major galaxy mergers. Finally, I will show how future data obtained combining observations with the ALMA radio telescope and the NuSTAR X-ray observatory will allow us to understand the physical details of the connection between black hole growth and galaxy evolution.

Abstract

How do the first galaxies form and evolve? Optical and near-infrared deep surveys are now finding galaxies at very high redshifts. However, they are typically small, not massive and present some but not very high star formation. But now the Herschel Multi-tiered Extragalactic Survey (HerMES), the largest project that has being carried out with the Herschel Space Observatory, in collaboration with other groups, has discovered a massive, maximum-starburst galaxy at a redshift of 6.34. The presence of galaxies like HFLS3 in the early Universe challenges current theories of galaxy fomation and evolution. I will describe the method we have developed to find these galaxies, the follow-up observations with different facilities and the main physical properties of this extreme object.

Abstract

As astrophysicists, we are used to extracting physical information from the observations. The usual procedure is to propose a parametric physical model to explain the observations and use the observations to infer the values of the parameters. However, in our noisy and ambiguous universe, the solution to the inference problem is usually non-unique or diffuse. For this reason, it is important that our inversion techniques give reliable results. In this talk I present a few recent results (dusty tori of AGN, magnetic fields in central stars of planetary nebulae, oscillations of coronal loops, signal detection) in which our group is applying Bayesian ideas to extract information from the observations.

Abstract

A serious limitation in the study of the Galactic inner halo and bulge globular clusters has been the existence of large and differential extinction by foreground dust. We have mapped the differential extinction and removed its effects, using a new dereddening technique, in a sample of 25 clusters in the direction of the inner Galaxy, observed in the optical using the Magellan 6.5m telescope and the Hubble Space Telescope. We have also observed a sample of 33 inner Galactic globular clusters in the framework of the VVV survey that is currently being conducted with the new Vista 4m telescope, in infrared bands where the extinction is highly reduced. Using these observations we have produced high quality color-magnitude diagrams of these poorly studied clusters that allow us to determine these clusters relative ages, distances and chemistry more accurately and to address important questions about the formation and the evolution of the inner Galaxy.

Abstract

The anomalous microwave emission (AME) is an additional diffuse foreground component, originated by an emission mechanism in the ISM different from the well-known synchrotron, free-free and thermal dust emissions. It was first discovered at the end of the nineties as a correlated signal between microwave CMB maps and infrared maps tracing the dust emission. Ever since several detections have been found in individual clouds in our Galaxy. This emission is an important contaminant for current and future CMB experiments, and therefore its characterization (both in temperature and in polarization) and understanding is mandatory. So far different theoretical models have been proposed to explain the physical mechanism that give rise to this emission. In this talk we will review these models and will present the current observational status of the AME, with particular emphasis on some recent studies that have been performed by our group in the IAC in the Perseus molecular complex and in the Pleiades reflection nebula.